Method of reinforcing a laminated member such as a skin for an aircraft

ABSTRACT

A method of reinforcing a laminated wing skin ( 10 ) for an aircraft. The method comprises laying-up a plurality of fibers to form the laminated wing skin ( 10 ). A composite reinforcement member ( 14 ) is positioned on a surface ( 16 ) of the laminated skin ( 10 ) and one or more further layers are laid up so as to enclose the composite reinforcing member ( 14 ) at a position adjacent one surface of the laminated skin ( 10 ).

This application is the US national phase of international applicationPCT/GB01/00469 filed 6 Feb. 2001, which designated the US.

The invention relates to a method of reinforcing a laminated skin for anaircraft.

An increase in local thickness of aircraft skin is often desirable,particularly to provide reinforcement around an access hole.

FIG. 1 is a cross section of a laminated skin for an aircraft reinforcedin a known manner.

Referring to FIG. 1, it is known to add reinforcement plies 1 to alaminated skin section 2 formed from layers 3 in order to increase thelocal thickness. The plies 1, which are formed from carbon fibrecomposite, glass fibre or aramid fibres, are generally buried spacedapart between successive layers 3 to define a reinforced area 4.

Where multiple reinforcement plies 1 are inserted between successivelayers 3, the multiple layers are effectively displaced from thecentroid of the skin section 2 which is not always desirable. Moreover,the separation of successive layers 3 by the reinforcement plies 1increases the possibility of peel-induced delamination of the skinsection 2.

An aim of the invention is to provide an improved method of reinforcinga laminated member for an aircraft.

According to a first aspect of the invention there is provided a methodof reinforcing a laminated member such as a skin for an aircraft, themethod comprising laying-up a plurality of layers to form part of thelaminated member, positioning a composite reinforcement member on alayer of the laminate member and laying-up one or more further layers soas to complete the laying up of the laminated member and enclose thecomposite reinforcing member at a position adjacent one surface of thecompleted laminated member.

In that way, instead of providing a plurality of reinforcement members,each being placed between different adjacent layers of the laminatedmember, only the single composite reinforcement member need be placedbetween the adjacent layers. Consequently, fewer layers of the laminatedmember are stepped, thereby making the laminated member morestructurally efficient and leading to performance benefits.

The method may include forming the composite reinforcement member from aplurality of layers, preferably at the same time that the laminatedmember is being produced in a parallel process. In that way, productiontime can be minimised. The finished composite reinforcement member canthen be introduced into the laminated member at a convenient time.

According to a second aspect of the invention there is provided alaminated member such as a skin for an aircraft reinforced using amethod according to the first aspect or any of the consistory clausesrelating thereto.

A method of reinforcing a laminated skin for an aircraft in accordancewith the invention will now be described by way of example and withreference to FIGS. 2 and 3 of the remaining accompanying drawings inwhich

FIG. 2 is a cross section through a laminated skin for an aircraftreinforced by a method in accordance with the invention,

FIG. 3 is a cross section through a laminated skin section made inaccordance with the invention and having an access hole formedtherethrough.

An aircraft wing skin 10 is of laminated form and is made from a lay-upof fibres so as to comprise a plurality of layers 12, each layer beinglaid in one of several different directions, for example at 0 degrees,45 degrees and −45 degrees, in known manner.

Referring to FIG. 2, a composite reinforcement member 14 is also madefrom a lay up of fibres so as to comprise a plurality of layers 16. Thelayers 16 may be arranged so as to form a reinforcement member 14 whichgenerally tapers towards an inner surface 18 of the wing skin 10.

In some applications, for example when reinforcing access holes inaircraft wing skins, many similar composite reinforcement members 14 arerequired. In such a case, the composite reinforcement members 14 can bemanufactured by an automated dedicated process.

The composite reinforcement member 14 may be produced in parallel with,and preferably at the same time as, the wing skin 10. In that way, thelead-time in manufacturing the wing skin 10 can be significantlyreduced.

The composite reinforcement member 14 is positioned on a layer 12 of thewing skin 10 just prior to the end of the wing skin lay-up process. Oncethe reinforcement member 14 has been placed in position, one or morefinal layers 12 are added to hold the composite reinforcement member 14firmly in place beneath and adjacent the inner surface 18 of the wingskin 10. By placing the reinforcement member 14 in the lay-up asdescribed with respect to FIG. 2, manufacturing and design issignificantly simplified and associated costs are reduced, together withthe risk of delamination when compared to the FIG. 1 arrangement.Moreover, fewer layers 12 are stepped from the centroid of the wing skin10 than in the FIG. 1 arrangement, thereby making the skin morestructurally efficient.

Referring to FIG. 3, once the wing skin lay-up process is completed, anaccess hole 20 may be formed through the composite reinforcement member14 and layers 12 of the wing skin 10.

The composite reinforcement member 14 may be made using a variety oftechnologies including pre peg, woven, braided, pultruded or any otherapplicable technology.

Whilst specific reference has been made to a laminated skin of anaircraft, the invention could be applied to laminated ribs or spars oranother member for an aircraft.

1. A method of reinforcing a laminated member for an aircraft, themethod comprising: laying-up a plurality of layers to form part of thelaminated member; forming a composite reinforcement member from aplurality of layers; after said forming step, positioning the compositereinforcement member on said part of the laminated member; and laying-upat least one further layer so as to complete the laying up of thelaminated member and enclose the composite reinforcing member at aposition adjacent one surface of the completed laminated member.
 2. Amethod according to claim 1, in which the method includes forming thecomposite reinforcement member at the same time as the laminated memberis produced in a parallel process.
 3. A method according to claim 1, inwhich the method includes forming an access hole through a part of thelaminated member which is reinforced by the composite reinforcementmember.
 4. A method of reinforcing a laminated member for an aircraft,the method comprising: laying-up a plurality of composite parallellayers to form part of the laminated member, said parallel layersproviding maximum tensile strength; forming a composite reinforcementmember from a plurality of layers; positioning the compositereinforcement member on said part of the laminated member; and laying-upat least one further layer so as to complete the laying up of thelaminated member and enclose the composite reinforcing member at aposition adjacent one surface of the completed laminated member.
 5. Amethod according to claim 4, in which the method includes forming thecomposite reinforcement member at the same time as the laminated memberis produced in a parallel process.
 6. A method according to claim 4, inwhich the method includes forming an access hole through a part of thelaminated member which is reinforced by the composite reinforcementmember.
 7. A laminated member for an aircraft reinforced using a methodaccording to claim
 4. 8. A method of reinforcing a laminated member foran aircraft, the method comprising: laying-up a plurality of compositeparallel layers to form part of the laminated member, said parallellayers providing maximum tensile strength; forming a compositereinforcement member from a plurality of layers; after said formingstep, positioning the composite reinforcement member on said part of thelaminated member; and laying-up at least one further layer so as tocomplete the laying up of the laminated member and enclose the compositereinforcing member at a position adjacent one surface of the completedlaminated member without compromising the tensile strength of said partof said laminated member.
 9. A method according to claim 8, in which themethod includes forming the composite reinforcement member at the sametime as the laminated member is produced in a parallel process.
 10. Amethod according to claim 8, in which the method includes forming anaccess hole through a part of the laminated member which is reinforcedby the composite reinforcement member.
 11. A laminated member for anaircraft reinforced using a method according to claim 9.